Crashing Question

yeehaanow

yeehaanow

Member
Murocflyer said:
Along the same lines, can you control a quad if a motor goes out? How about a hexicopter? Can you limp in for a landing?

Thanks,

Frank
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I have no faith in a hex being savable. I've heard enough stories to think that your chances are better on an octo. Also depends on the controller.
 

L

Lifter

Member
R_Lefebvre said:
What happens in a MR if a battery fails, but you have two batteries in parallel? Does the first battery take down the second? I'd think the battery that is failing will stop outputting amps as the voltage drops, just basic electrical theory, and you'd be flying on the first battery only. So you'd see a rapid power loss, but should be saveable?
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Have had this happen repeatedly but not everytime on an Octo, right from the first flight, all Deans connectors done by the Pro's - two batteries in parallel.
In my case 1 battery gets sucked dry but were lucky enough to land before total power loss since it was new and was still testing things out.
Put the HK Lv screamers on and that certainly helped but didn't fix the prob obviously, swapped out leads changed Deans plugs still the same issue 50% of the time.

Threw all the Deans leads away fitted EC5's, problem gone.

The question was " Does the first battery take down the second" in my case no it did not but I guess it could - it sure stuffed a few 4500 Nanos and 1 Thunder Power 5000mah though. (replaced by Tp)
Voltage check after the event(s) 1 battery dead flat the other still fully charged.

Just my experience....
 

S

Stacky

Member
yeehaanow said:
Nice save Stacky! That's what you call JeLLoooo!
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Not my video, a local guy who has a ton of flying experience who could probably land anything. I could never have landed that quad and its the only video I know of where someone has been able to land a quad when a prop has broken in flight.
Personally I could never save a quad if a motor or prop gave out, I would have a 5% chance of saving a Hexa and I havent flown an Octo apart from a x8 but there is plenty of video out there of octos surviving. I havent seen any video of anyone saving a Hexa with a motor or prop problem but I suspect they are out there somewhere. Lots of people can take off with a missing prop but having something die in flight is another story. I have landed a X8 when a prop broke in flight though. (badly)
 

S

Str8 Up

Member
I apologize but I don't follow some of the logic here. The thread is about avoiding crashes. As a point of reference I mentioned that I have not had a crash with any of my SR helis in seven years. This represents over a thousand AP flights. I am then informed that MR's are far more reliable due to fewer single points of failure. If this is so, then there is no excuse to ever crash a MR. From this I can only draw the following conclusions:

1. I am a genious (not even close)
2. Many MR pilots are too careless
3. MR technology has not fully matured for good reliability
4. MR's are not more reliable than SR helis but rather have just as many failure points, just different types.

Take your pick.

My point is not to directly debate SR versus MR reliability, but rather to say that all crashes are avoidable if the necessary amount of thought and effort is placed on doing so. The basic airframes we use to fly Red cameras I have been flying for 10 years now. What you fail to understand is almost every "single point of failure" can be visually inspected or tested, if you know what to look for and bother to take the time. This is a little more challenging when it comes to mainly circuitry and firmware. I never minded chasing mechanical issues, but electronic issues were always a real pain.
 

D

Dewster

Member
The biggest culprit for crashes are from cheap props breaking in flight. It's not the cost, but the quality of prop construction. By far most of these crashes are from quads and hexas losing one in flight. I don't know what's better: a craft that drops straight down from the sky or one that's on a glide slope to who knows where. Start building with proven, reliable parts. For props it's Graupners, or APC. Just picking the right props will prevent so many from having crashes.

I never flew my craft into any objects or had any hard landings that were under my control. My flat hexa flew like a dream..until an expensive, cheap made prop failed on me.
 


R

R_Lefebvre

Arducopter Developer
Str8 Up said:
I apologize but I don't follow some of the logic here. The thread is about avoiding crashes. As a point of reference I mentioned that I have not had a crash with any of my SR helis in seven years. This represents over a thousand AP flights. I am then informed that MR's are far more reliable due to fewer single points of failure. If this is so, then there is no excuse to ever crash a MR. From this I can only draw the following conclusions:

1. I am a genious (not even close)
2. Many MR pilots are too careless
3. MR technology has not fully matured for good reliability
4. MR's are not more reliable than SR helis but rather have just as many failure points, just different types.

Take your pick.

My point is not to directly debate SR versus MR reliability, but rather to say that all crashes are avoidable if the necessary amount of thought and effort is placed on doing so. The basic airframes we use to fly Red cameras I have been flying for 10 years now. What you fail to understand is almost every "single point of failure" can be visually inspected or tested, if you know what to look for and bother to take the time. This is a little more challenging when it comes to mainly circuitry and firmware. I never minded chasing mechanical issues, but electronic issues were always a real pain.
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I'm not arguing, your points are all very logical. I would like to ask however, how exactly do you "inspect" a servo? A heli has 4 servos, each of which are single points of failure. Inside of each servo, you have many of the same electrical systems that you have in each power unit of a MR. I'd think this presents exactly the same failure potential as a MR power unit. But on top of that, you also have a bunch of gears. That's even more failure points. Regardless, how do you inspect a servo? The answer is, you can't.

I think what is happening, is that you are probably using high quality servos, which are well engineered, and have a very high MTBF. It's really the only explanation.

To your points:

1. I can't say, but it sounds like you're at least successful, so that's saying something.
2. This is probably true in the majority of cases of MR crashes you hear about. For example, I've had two MR crashes. One of them I was fooling around in my back yard which is surrounded by trees, by flying up, and then shutting off the engines and letting it tumble, then restarting them and having it recover itself. One of these times, when it restarted, it completely sideways, and ended up flying into a tree. But this is not the MR's fault. I would never fly my helis like this.
3. Absolutely!!! For the most part we are stuck using propellers that are COMPLETELY inadequate. These props are not designed for MR's, they are designed for slow flying airplanes, hence the name. My second crash, was when I was doing some aerobatics with the quad, and prop blew apart. First time for me, but it was instant crash. This is somewhat akin to using cheap linkages on your heli.
4. This I completely disagree with. It's just not true. An Octocopter has very few single points of failure. None of the power units is a SPF. None of my battery connectors are (they're all doubled up). Really, the only SPF are all the pieces in line with the flight controller. So, the FC itself, obviously (which is no more complicated than a FBL controller), the power supply for the FC, the wire between the FC and power supply, the wire between the power supply and battery. Note, 3/4 of those SPF's could be removed easily. Two batteries, two regulators, two wire sets, and then a power supply switchover build onto the board. You may think the FC is a huge SPF, but IMO, it actually removes quite a few other SPF. Namely, my Rx and Tx. If either goes down, the copter will land safely.

So again, to recap:

Quads have 4 SPF power units.
Hexas have 6 SPF, since most don't stand a chance of surviving a failure. Hexas are WORSE than quads, if they are not proven to be flyable with a motor out.
Octos have 8 SPF IF they are not proven flyable with one unit gone, and most are like this. This is the case if say, you're flying a really heavy payload like a RED, and you haven't tested it. Personally, I think most people haven't done this, there's little chance those Octos can fly with that payload. If it takes more than 60% throttle to hover with your payload, you're probably doomed.

However, if your Octo CAN fly with one motor out, then it has NO SPF power units.

A helicopter has 4 SPF servos, which are literally, black boxes. All the linkages (easy to inspect). And it's full of Jesus bolts. Jesus bolts top and bottom, two in the feathering shaft, the rudder feathering shaft, rudder set screw, I could go on and on... The only saving grace here, is that the MTBF on these is high if you use quality components, and most are easy to inspect and be sure they are right.
 

R

R_Lefebvre

Arducopter Developer
Str8 Up said:
Why don't you do an overspeed proof test on all new props?
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On each unit, before putting it into service? Well, one problem is that the props have a finite fatigue life, and you would have just used up a bunch of it.

If you are talking about just doing sample and determining statistical reliability... yeah, we should do that. Problem is that there are too many "no name" props out there. I plan on sticking with APC and/or Graupner. No guarantees, but a name you can stand behind.
 

R

R_Lefebvre

Arducopter Developer

yeehaanow

yeehaanow

Member
Str8 Up said:
What you fail to understand is almost every "single point of failure" can be visually inspected or tested, if you know what to look for and bother to take the time. This is a little more challenging when it comes to mainly circuitry and firmware. I never minded chasing mechanical issues, but electronic issues were always a real pain.
Click to expand...

Key word is almost. But as they say... $hit happens.
Full-scale planes and copters crash, RC planes and copters crash. It cannot be prevented 100% of the time, which is why we should always fly with this in mind.
 


S

Str8 Up

Member



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